linux-kernel - Re: [PATCH] x86, perf, nmi: Disable perf if counters are not accessable

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Date:	Tue, 23 Nov 2010 22:18:01 +0300
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Don Zickus <dzickus@...hat.com>, sedat.dilek@...il.com,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] x86, perf, nmi: Disable perf if counters are not
	accessable

On Tue, Nov 23, 2010 at 08:07:47PM +0100, Peter Zijlstra wrote:
> On Tue, 2010-11-23 at 22:04 +0300, Cyrill Gorcunov wrote:
> > On Tue, Nov 23, 2010 at 07:27:07PM +0100, Peter Zijlstra wrote:
> > > On Tue, 2010-11-23 at 19:21 +0100, Sedat Dilek wrote:
> > > > Due to BIOS l(ocal)apic is not possible:
> > > > 
> > > > # dmesg | grep -i apic
> > > > [    0.000000] Using APIC driver default
> > > > [    0.000000] Local APIC disabled by BIOS -- you can enable it with "lapic"
> > > > [    0.000000] APIC: disable apic facility
> > > > [    0.000000] APIC: switched to apic NOOP
> > > > [    0.008891] no APIC, boot with the "lapic" boot parameter to force-enable it.
> > > > [    0.036141] Local APIC not detected. Using dummy APIC emulation. 
> > > 
> > > Have you tried booting with "lapic" as the second last msg suggests you
> > > do?
> > 
> >  Peter, Don, might not we need something like the patch below -- ie to check for
> > apic earlier and do not acquire cpu for PERF cpu bit, and its cpu model, etc
> > if there is no active apic? And perhaps for nmi-watchdog, we should not try
> > to creat perf event for same reason and simply report that nmi-watchdog is
> > disabled (though of course hpet based one should try to continue).
> > 
> >  No?
> > 
> 
> Ah, no.. now I get what you mean.
> 
> We can use the pmu without interrupt with we miss the lapic, that is
> perf-stat will still work.
> 

Yeah, I forgot about perf-stat

 Cyrill
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